It shows Amazon is serious about its Android App Store and has made sure it launches with a can’t-miss title. Few games are as popular as Angry Birds, which has been downloaded now 100 million times. There are still a number of questions surrounding Amazon’s Android app store, but grabbing an exclusive like this should be an easy way to introduce the store to millions of users, who will no doubt show up to get the next version of the game. It’s unclear if Amazon paid for the exclusive rights to Rio, and there’s no word how long the exclusive period lasts.

In the case of the Angry Birds launch on Android, GetJar, the independent store, was supposed to get a 24-hour exclusive launch window before the game appeared on Android Market. But crushing demand prompted Rovio to ask GetJar to open downloads on Android Market early. Still, GetJar saw a huge bump in visitors, with traffic up tenfold in that first day. That’s why this is a savvy move for Amazon. Even if it did pay for the rights, it will certainly be worth it for the amount of customers who will show up.

The launch also highlights the importance of third-party app stores. Developers are increasingly being confronted with app store options, which can be confusing. But with some big options like Amazon emerging, it gives developers new channels to sell apps. And it means that there’s a better chance their apps will be promoted beyond anything Google does in Android Market. People already trust Amazon for online purchases, so opening an app store makes a lot of sense. Now developers will be able to tap into that experience to sell apps.